The first thing you see upon arrival at GitHub's brand new San Francisco headquarters is Ryan Tomayko's Macbook Pro. This beat-up old laptop is where Tomayko, one of the company's first engineers, created the "pull request" -- the all-important way of contributing software code (and all sorts of other stuff) to projects housed on the company's web service, a contraption that has redefined the way the world builds things.
The Macbook is considered an historic artifact, and it's preserved as a museum piece. You can still see the black duct tape that Tomayko stuck on the left side of the machine to keep it from shocking him, covering a spot where his hands had worn down the machine's metal casing.